1912-1922 20¢ Franklin
(read how to identify your stamp below)
This is the 20¢ Franklin. It is quite common and usually worth no more than a couple of dollars when used, however it can have reasonable value when unused. As there are only four variations of this stamp, identification is relatively easy.
DETERMINING THE PERFORATIONS
Count the perforations along the bottom, its as simple as that! Below is a chart indicating the perforations of each Stamps Catalog #.
As you can see both catalog number 438 and 476 have the same number of perforations. How does one tell them apart? The difference is that one has a watermark and one does not.
DETERMINING THE WATERMARK
To know which watermark a stamp has, one needs watermark fluid or lighter fluid (both of these are extremely flammable and should be used with extreme caution, outside, in a safe area far away from combustible materials). Soak the stamp in the fluid in small plate with a black or very dark color. The watermark will show, sometimes faintly by looking at the back of the stamp. The watermark fluid will quickly evaporate from the stamp, leaving the stamp and its gum intact.
If there is a watermark on the stamp the watermark will show part or all of a letter U, S or P. See illustration below